1. Field of the Invention
This invention relates to a setting device for a protective control system for effecting the protective control of a power transmission system or the like by using a digital arithmatic processing unit such as a microcomputer.
2. Description of the Prior Art
In the prior-art protective control system, for instance, a protective relay system used for a power transmission system, setting taps, rotary switches and variable resistors are provided for distance relay elements, overvoltage relay elements etc., and overcurrent relay elements so that the value for each element can be independently set. For example, in a distance protective relay system for protecting a power transmission line, overcurrent relays, undervoltage relays, mho relays, reactance relays, earthing overvoltage relays, directional relays, etc., are used in combination. In such protective relay systems, there are sometimes several tens of setting values to be set for respective relay elements included in the system. In addition, the individual setting values vary with the system in which the protective system is employed. The setting operation therefore requires the calculations of a highly skilled engineer.
In light of the recent progress in digital data processing techniques, the incorporation of digital arithmetic processing units such as microcomputors, in such protective control systems has been proposed. A great advantage of such a digital protective control system is that a number of its elements can be processed with the same hardware after a combination of programs is stored in the digital arithmetic processing unit. Thus, the size of the system can be reduced, compared to that of the prior art which is constructed by combining a number of protective relay element circuits.
However, it is undesirable from the standpoint of size reduction for a number of setting sections for respective relay elements to be provided in such a digital protective control system. Accordingly, a system in which a plurality of setting values are written from a single setting section to a memory within a digital processing unit and selectively read out when required is under consideration. Such setting systems are basically classed into two types, depending upon the kind of the memory used.
Namely, one system uses the random access memory (RAM), a memory capable of reading and writing data at any time. A drawback in this system is that the data memorized in the RAM is erased when a power source connected thereto is lost. In other words, when the power source is lost or removed due to power failure or maintenance of the system, it is necessary to set a plurality of values. This is a very cumbersome and impractical process.
The other system uses the read only memory (ROM). As with ROM, commonly termed IC memories are used in cases in which such memories are assembled in microcomputors or the like in order to meet the requirements for miniaturization. Data which has been once written in the ROM will not be lost even when the power source fails. However, an exclusive writing unit called an ROM writer is necessary in order to write in the data. Furthermore, once the data has been written it cannot be easily changed. This is very inconvenient in view of the maintenance and application of the system.
Still further, in either of these two system the normal operation as the protective control system must be stopped when changing a setting value. A power transmission system or the like which is protected by the protective control system fails to be protected during this period. This is inconvenient in view of the maintenance.
An object of the invention, accordingly, is to provide a setting device for a protective control system, with which the setting and alteration of setting values can be readily made and with which the setting value once memorized, is not lost even when the power source is lost, and the regular protective control function of which is maintained even when changing a setting value.
According to the invention, the above object is achieved by a setting device for a protective control system, which comprises first and second non-volatile memories, a control signal generating means for controlling the preservation and erasion of the data stored in the first and second non-volatile memories, a setting section for producing setting value data to be memorized in the first non-volatile memory, a means for writing the setting value data in the first non-volatile memory, means for causing the setting value data memorized in the first non-volatile memory to be read out therefrom and transferred to and memorized in the second non-volatile memory, and a processing section for effecting arithmetic processing for protective control by reading out memorized data from at least either one of the first and second memories.